IEEE P1149.4 Mixed-Signal Test Bus Working Group
Meeting Minutes
for
October 22, 1995
Generously sponsored by Hewlett-Packard
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Meeting Agenda
Time Topic Responsibility
8:00am Arrival and introductions Adam Cron
8:15am Approval of May, 1995 minutes Adam Cron
8:30am Presentation of the proposal made to 1149.1 Lee Whetsel
9:30am .1/.4 overlap strategy/positioning Gordon Robinson
Ken Parker
10:00am Break - Thank you Hewlett-Packard
10:30am 1149.1/P1149.4 overlap - continued
11:00am AB/AT switches (calibration suite) Steve Sunter
Brian Wilkins
11:45am Patent follow-up Mani Soma
12:00pm Lunch - Thank-you Hewlett-Packard
1:00pm Variable Vref - How might we support it? Lee Whetsel
Steve Sunter
1:45pm Differential cells Steve Sunter
2:30pm IIC - Formal Response Frans de Jong
2:45pm IC progress report Keith Lofstrom
3:00pm Break - Thank you Hewlett-Packard
3:30pm Internal Control Cells Charles Meyerson
4:15pm Draft D05 progress report Brian Wilkins
5:00pm Cost calculations for adding P1149.4 Steve Sunter
5:20pm Balloting schedule Adam Cron
5:40pm 1149.n updates Anyone
5:55pm Next meeting in Scotts Valley, CA in February, Adam Cron
1996
6:00pm Adjourn Adam Cron
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In addition, I would like to add a section in the afternoon which confronts
the Instruction Definition issue head on. Ken Parker proposed a selection
of instructions: the three mandatory instructions from 1149.1, and one he
calls AFUNCTION. Ken proposed the behavior and changes to the current ABM
to support his proposal. Ken will lead this discussion in the afternoon
after the Internal Control Cells and Draft D05 progress report discussions.
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Working Group Statistics
Working Group Members 35
Total Subscribers 257
Countries Participating ~23
Companies Participating ~158
Funds Available $2219.99
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Meeting Attendees
Name Company Sponsor
Terry Borroz Teradyne, Inc.
Bill Coombe Medtronic
Bernard Courtois Institut National Polytechnique de Grenoble
Adam Cron Motorola
Dan Dandapani University of Colorado
Frans de Jong Philips Electronic Design & Tools
Steve Dollens International Microelectronic Products
Tom Fisher Delco Electronics
Allen Heiden Motorola
Madhuri Jarwala AT&T Bell Laboratories
Terry Junge Seagate International
Jake Karrfalt Alternative System Concepts
Mehdi Katoozi Boeing
Keith Lofstrom KLIC
Colin Maunder British Telecom
Charles Meyerson Medtronic
Benoit Nadeau-Dostie LV Software Canada Inc.
Naveena Nagi LogicVision
Elbert Nhan Johns Hopkins University
Stig Oresjo Hewlett-Packard
Ken Parker Hewlett-Packard
Michel Parot Thomson-CSF
Gordon Robinson GenRad
Mani Soma University of Washington
Steve Sunter Nortel
Lee Whetsel Texas Instruments
Brian Wilkins Southampton University
Sending Regrets
Name
Company Sponsor
John Andrews
National Semiconductor
Nai-Chi Lee
Philips
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Arrival and introductions
The Working Group thanked Hewlett-Packard for sponsoring this meeting.
Stig Oresjo announced he is retiring from the P1149.4 Working Group but
will continue working with the Working Group on P1149.4 manufacturing
issues. Stig presented the Working Group with a formal resignation letter
wishing us "all the luck in the future".
Gordon Robinson motioned to thank Stig for his work with P1149.4. Seconded.
Unanimous approval.
Approval of May, 1995 minutes
Adam Cron motioned to approve the May, 1995 minutes. Seconded. Unanimous
approval.
Presentation of the proposal made to 1149.1
Lee Whetsel's Presentation to 1149.1.
Brief background: At the Portland Oregon P1149.4 meeting Lee mentioned he'd
been working on simple 1149.1 compliant analog cells that don't have
measurement circuitry and AB1&2 pin requirements. Lee suggested P1149.4
make these cells and the 4 pin TAP they require the baseline for P1149.4,
to address interconnect testing of pin limited ICs. P1149.4 rejected this
suggestion since P1149.4's objective is for full analog testing using the
currently defined cell and 6 pin TAP interface. Lee told P1149.4 he was
going to propose the simple cells to 1149.1. P1149.4 endorsed this action
by Lee. At the Portland Maine 1149.1 meeting, Lee presented the simple
analog cells for the first time. They were well received by 1149.1. At ITC,
Lee repeated the cell presentation to P1149.4 accompanied by a paper
detailing how 1149.1 and P1149.4 could cooperatively develop a Mixed-Signal
Test Bus Standard.
REFER TO LEE'S VIEWGRAPHS:
Figure 1 shows the current 1149.1 requirements for mixed-signal
boundary-scan (one test cell is required for each digital I/O and n test
cells are required for each analog I/O; at least 4 pins for the test bus).
Figure 3 illustrates the test method using the current 1149.1 structure (2
test cells for each digital interconnect and 2 groups of n test cells for
each analog interconnect). Figure 2 presents the likely future mixed-signal
boundary-scan scheme for P1149.4 (only one test cell is required for each
digital or analog I/O, and the test bus requires at least 6 pins). Figure 4
shows when using the P1149.4 test method, one would need only 2 test cells
for each digital or analog interconnect. Figure 5 combines the current
1149.1 structure with future P1149.4 structure which means each P1149.4
analog I/O pin would be regulated by 1 test cell while each 1149.1 analog
I/O pin would be regulated by n test cells. Figure 6 reconciles the
difference between 1149.1 and P1149.4 by making each P1149.4 AND 1149.1
analog I/O regulated by 1 test cell with an option for partitioning. One
test cell is now needed on 1149.1 analog I/O pins to control and observe
data.
Figures 7, 8, and 9 represent 1149.1 compliant 2-state and 3-state output
analog test cells, as well as bi-directional test cells. Figure 10 shows a
1149.1 compliant analog input test cell. Figures 10 and 11 detail the
1149.1 compliant analog input and output test cells, respectively. Figure
13 shows how 2 analog output cells may be connected between the mixed
signal circuit and the pin, and still comply to 1149.1. The details of the
cells in Figure 13 are shown in Figure 14.
Ken had a question about Figure 13's S2 and S3 "small" switches; full
capability of the pin driver is still available. Mani Soma asked if V+ and
V- is programmable. The answer is whatever voltages it takes to make the
output go to Vmin and Vmax. Mehdi commented that if an analog circuit is
connected to a digital circuit, the minimum and maximum excursions of the
analog voltages could hurt the digital circuit. Steve Sunter said this is
just an implementation example. In Figure 12, the switch is conceptual.
Figure 13 shows optimized 1149.1 compliant bi-directional analog test
cells. This scheme simulates 1149.1 bi-directional test cells. Colin
Maunder cautioned that we not only need to be concerned with "low level"
tests, but also a "higher level" of testing. Lee said this is 1149.1's way
of testing simple interconnects and shorts, but Colin disagreed. Adam
interjected that Lee's proposal is to implement how 1149.1 is doing test
(to make a clean break between 1149.1 and P1149.4), and P1149.4 's job,
according to Lee, is to complete the scheme for mixed-signal testing. Ken
commented that Lee's proposal is just to test simple wires and
interconnects, but Colin said we need to be clear on how to test all kinds
of components, not just simple wires. Colin said SAMPLE/PRELOAD
instructions are for logical level tests only. Ken explains when an P1149.4
chip is trying to "listen to" an 1149.1 chip, at this moment there is no
way to do that unless one implements Lee's scheme or some other method.
Mani asked, when Lee presented this to 1149.1, what the reaction/response
was. Lee Whetsel said 1149.1 readily embraced it but Gordon Robinson
proposed forming a study team to discuss this subject. Overall, the
response was favorable.
Next, Lee showed viewgraphs of the diagrams found in his 9/21/95 paper
entitled "Proposal to Simplify Development of a Mixed Signal Test
Standard." Figure 1 in the paper presents analog output/input test cells
that exist between mixed signal circuit input/output pins. The cells can be
as simple as two switches and a TAP control. Figure 2 is a diagram of a
possible 1149.1 2-state cell (full-time drive and not tri-statable) between
the mixed signal circuit and an output pin. An improvement can be made to
this cell by feeding the output back to the cell for observing. Figure 3 is
basically identical to Figure 2 except another cell is added to control the
3-state output amplifier (3SOA); an example of the cells is similar to
Figure 11 in Lee's viewgraphs of the proposal made to 1149.1. For
bi-directionality, just add a 3-state input amplifier (3SIA) to the
structure in Figure 3. Ken said the scheme presented in Figure 3 is
sufficient for most bi-directional purposes unless one needs to put the
circuit into a quiescent state. Figure 5: For inputs, use one 1149.1 AITC
as a capture cell. The 3SIA is used during test mode to isolate input
signal data from the core and allow the AITC to capture and shift out
analog signal data at the input pin. Figure 6: The shaded blocks are what
P1149.4 needs to make its measurements. There were comments on the need to
have clear descriptions of instructions. Questions were raised about the
need for 3SIA/3SOA because sometimes only passive components are hanging at
the pin. Ken reminded that Lee's presentation is predicated on testing
simple wires and interconnects. Lee said this is a "what if" presentation.
What if you have 1149.1/.4 chips talking/listening to each other, then what
are the cells/circuitry required by P1149.4 to do P1149.4 measurements?
Figure 7 shows how to upgrade 1149.1 3-state pins to P1149.4. Again, the
shaded blocks are what P1149.4 needs to complement 1149.1 3-state circuitry
which only provides 1, 0, and disable. Figure 8 is for bi-directionality.
Figure 9: upgrading 1149.1 inputs to P1149.4. This is by far the most
expensive upgrade of all since 1149.1 only provides an 3SIA, and we also
need the rest of the structure for P1149.4 measurement capabilities.
Adam commented that he has concerns about 4 pins vs. 6 pins. We might not
have chips with 6 pins (P1149.4) out there if developers can only afford 4
pins (1149.1). But one never knows. Madhuri said Lee's schemes might not be
useful since they are only for testing simple wires. Keith Lofstrom
commented that when adding all this additional circuitry, there may not be
enough drive. The 1149.1 by itself doesn't drive but the upgrade version
does (Figure 9). Brian Wilkins agreed with Lee's proposal. The problem is
what we can assume about what 1149.1 will include in its standard. The
worst scenario is that we have to throw away the current P1149.4 draft.
Miscellaneous comments that P1149.4 will not allow partitioning. Colin
reiterated that we must understand what we are doing (testing)? We would
need to break our objectives down one by one and put the bits and pieces
together. Ken said that was why few years ago, he advocated putting 1149.1
on all pins and optionally P1149.4 layer can be added as needed.
Adam summarized: Just focus on capabilities, not on the number of bits. Be
general and flexible. We need to keep going with what we're doing since
1149.1 has not voted on Lee's proposal.
Steve said that if you want analog G, it must be the P1149.4 "G", not
1149.1 logic 0, since 1149.1 does not have sufficiently stable or enough
drive in some instances. Lee said he thinks 1149.1 should accept his
proposed test cells as a requirement on every pin. Gordon commented that
the highest level of testability is P1149.4 today on pin by pin basis. He
outlined 4 levels of testability: 1) does nothing, 2) 1149.1 capability, 3)
analog 1149.1 capability, or 4) full P1149.4 capability. Designers should
be allowed to use any of these on a pin by pin basis. Colin said we should
decide which instructions should be mandatory and which are mandatory only
in certain cases. Colin advocated establishing a much clearer definition of
"EXTEST". His opinion is that EXTEST should include more than just simple
interconnect test. Madhuri again voiced concern that Lee's proposal only
covers the simple cases of wires & shorts. His proposal would test maybe 50
to 70 % of all analog interconnects. Steve said we can extend 1149.1's
definition of logic high/low to Vmax/Vmin. There are 3 options: 1) no
boundary scan, 2) 1149.1, and 3) P1149.4. In 1149.1 chips, make 1149.1
capability on analog pins optional. In P1149.4 chips, all P1149.4 pins must
have 1149.1. Gordon suggested motioning joint 1149.1/P1149.4 members to
propose changes to 1149.1. Brian agreed there is a need for a clear
definition of 1149.1 test. Perhaps we should quit talking about putting
1149.1 or P1149.4 on this or that pin.
SUMMARY: Lee discussed the proposal of changes to be made in 1149.1
presented to the 1149.1 Working Group in July. The response of 1149.1 so
far seemed favorable but no action has been taken on it. In the P1149.4
Working Group, there was both support for and opposition to the concept of
pin-by-pin classification. There were concerns about the
practicality/usefulness of Lee's proposal as it only covers simple
interconnects.
.1/.4 overlap strategy/positioning
1149.1/P1149.4 overlap.
Ken motioned to invite 1149.1 Working Group members to discuss joint
1149.1/P1149.4 issues sometime in the future. Seconded. Discussion
followed. We should do as much as we can at this meeting and at the 1149.1
meeting on Thursday. They (1149.1 Working Group) may decline our
invitation. Steve openly worried about implications of such a joint
meeting, because we would end up discussing only digital issues. Suggestion
that this could be a different meeting from the Scotts Valley meeting. Lee
proposed having a meeting SOON to achieve real progress. Ken said he would
love to see progress but thought that we are still far away from balloting.
Gordon pointed out there are 2 simple issues. Let's get a group decision on
where to start. If we can arrive at common grounds on what we want, then on
Thursday, we can raise it at the 1149.1 Working Group meeting. We need, at
that point, to have everyone in 1149.1 involved and vote on the relevant
issues. Maybe a 1149.1/P1149.4 meeting can be arranged for 2 hours. Colin
suggested to break into little subgroups and focus on specific issues and
have the subgroups report back to our Working Group. Gordon said let's make
assumption to have a group meeting and let's make it clear which issues
we're disagreeing about and only then it makes sense to have the meeting.
People who felt strongly about the issues should make the meeting. As a
result, a revised motion was on the table for having a joint 1149.1/P1149.4
meeting between after 6:00PM today and sometime during ITC. Gordon
suggested getting 6 people to get together and work on a specific set of
proposals before the 1149.1 meeting on Thursday. Lee said he would like to
recommend to 1149.1: Let 1149.1 do the digital part of P1149.4
(update/capture); a required feature of the infrastructure on 1149.1 chips.
Then there was discussion about level of revision of BSDL for old and new
chips (i.e. A-compliant, B-compliant, or C-compliant).
Ken withdrew the previous motion now that a small subgroup will soon be
formed to work on proposing to the 1149.1 on Thursday. Adam asked who would
like to be in the subgroup: Steve Sunter, Colin Maunder, Brian Wilkins, Lee
Whetsel, Ken Parker, and Madhuri Jarwala.
SUMMARY: The Working Group decided, after deliberations, to form a small
subgroup to outline 1149.1/P1149.4 issues that would be presented to 1149.1
at the 1149.1 Working Group meeting on Thursday. The idea is to make
recommendations to 1149.1 based on Lee's proposal to have changes in the
1149.1 Standard made so that P1149.4 would be compatible with 1149.1.
AB/AT switches (calibration suite)
AB/AT calibration suite (Refer to Steve Sunter's handouts).
Steve put up a viewgraph which contained basically what Brian put in the
draft with a little modification. In viewgraph 1 (Connecting AT pins to AB
buses), item (i): Steve recommended not to leave the internal analog test
bus in high-impedance state (good design practice but not essential for
proper P1149.4 operation). It should not be a requirement (that's why the
word "should"). Colin asked what it is we are trying to achieve with this
recommendation. He said we should not describe a way to get there. Steve
replied that it's just a note. Mehdi was concerned about how disconnecting
AT and AB busses would affect the operation of other chips. Ken said by
definition, core disconnect implies no effect on other chips. After more
debating, it was agreed that (i) be deleted.
Item (ii): Modified to read: "It shall be possible to electrically connect
and disconnect each internal analog test bus line (AB1 and AB2) to its
corresponding ETAP pin (AT1 and AT2 respectively)." Colin commented that
the wording "connect" and "disconnect" imply implementation details
involving switches which may not be the only way to implement it. Steve
responded by saying let's make the switches conceptual. Ken asked how about
changing to "isolate electrically". The final consensus was to leave it to
Brian to work out the wording.
Item (iii): Modified to read: "It shall be possible to provide a path from
the AT1 pin to the AT2 pin, without enabling other connections to permit
testing of the AT1 and AT2 buses." The motivation is to allow the integrity
of the bus infrastructure (wire paths on-chip and off-chip) to be verified.
Colin said what if the 2 buses are swapped, there is no way to find out at
this moment. After discussions, "AT1 & AT2", the board level busses, were
added between the words "the" and "buses" as shown above. Colin said maybe
we need to define what the specific instruction is to do this with. Steve
said let's defer the discussion on specific instructions since we may have
3 or 4 separate instructions that require (iii). The words "internal
voltages" mean the AB busses are connected to internal voltage references,
according to Mehdi. So "to the pins or internal voltage" was taken out. The
original motivation for the deleted phrase was to allow designers' ad-hoc
connections. Dan suggested that since all these are instruction-related,
perhaps we should wait until discussion of instruction to vote on these
items. Keith asked if the Working Group could discuss instructions now so
that we can be in the position to act on Steve's recommendations. However,
Steve preferred to continue with what he has and defer on motioning.
Item (iv): Ken said we might not need both G and +V for calibration
purpose. AT1 can be treated as an 1149.1 analog input and AT2 as an 1149.1
analog output. AT1 will meet requirements for 1149.1 analog input, while
AT2 will meet requirements for 1149.1 output analog output. Therefore,
AT1/AT1 comply with 1149.1 (under EXTEST?). It soon became clear that this
item will have to be revisited sometime in the future.
SUMMARY: (Refer to Steve Sunter's viewgraph 1) The WG agreed (i) is just a
note and will be modified by Ken Parker in the afternoon. Items (ii) &
(iii) are agreed upon as capabilities and (iv) tabled for discussion later.
Instruction Definition
Ken Parker 's unscheduled presentation.
Ken initiated a motion which is referenced to Steve's (i) discussed this
morning in his viewgraph 1.
MOTION: Given the ability to disconnect ABn from ATn, the state of ABn
shall have no effect on either the normal or test operation of the device
when ABn is disconnected. Motion was amended by deleting the phrase "the
state of" as suggested by Lee Whetsel. Note: AB is internal bus of device
and AT is the external bus to pin. Motion was seconded. Aye: 16. NO. 0.
Abstention: 1. Motion carried.
Referring to handout of e-mail with subject "Last minute mail...". This is
functionally equivalent to Brian's scheme in the draft D05 Figure 10.
However, this design is not compatible with existing 1149.1 software and
doesn't meet definition of BYPASS and SAMPLE. This design is also not an
"idiot-proof" scheme (people might do things to the flip-flops which can
affect the pins even though we are in the BYPASS mode). A modified Figure
10 of the same ABM is shown on the reverse side of Ken's Figure 10 handout.
It has a self monitoring output cell. CAPTURE/UPDATE flip-flops are by
definition boundary-scan cells. The TAP has a new output called AFUNC. The
interesting thing is that in EXTEST mode, the S1 and S2 switches are for
data and enable in pseudo 1149.1 test mode, and if neither is on, then it's
tri-state. Now in parametric test, we can enable AB1 and AB2. The same
EXTEST instruction can control both pseudo-.1 test and parametric test.
This supports 1149.1 software, meets BYPASS & SAMPLE rules and implements
analog SAMPLE, etc. In effect, Ken is proposing that EXTEST has the dual
role (expansion of definition) of pseudo-.1 and parametric tests. Try to
keep the instruction count as low as possible. In addition, with this
design, one can do other things off-chip.
Question: If we took AB1 and AB2 and the last bit (flip-flop Z) out of
Ken's ABM, are we left with something similar to Lee's proposal? Ken said
there are other simplifications such as merging the AND gates into the
driver. Adam asked Ken if he is showing the implementation details with his
diagram? Ken said Figure 10 of Brian's draft is inconsistent with what's
been said and he is trying to make the little changes to make it
consistent. This is indeed an implementation example. What we should be
able to do is to write down a set of rules based on this example without
showing it.
Ken's initial definition of EXTEST: Both pseudo-.1 and parametric tests. A
lot of integrity checking goes on during normal chip operation, at least in
1149.1. So, we need an integrity checking function to check the chip. We
don't need a separate EXTEST instruction to check the integrity of AT
busses. This diagram will not be part of the Standard, but stands as an
example. We need nomenclature for the "X", "Y", and "Z" flip-flops (memory
elements) for the Standard.
A question arose as to whether one can fan-out the enable control bit to
other pins to save some bits. The answer is "no" since one may want to
independently control switches at each pin. However, 1149.1 allows
paralleling the pins. This is a typical example of P1149.4 and 1149.1 not
merging smoothly. Steve Sunter suggested to vote on this. But Ken said
someone should double check his work. Steve said he completely agrees with
Ken's scheme because it's consistent with previous work Steve had done.
A motion was on the floor to vote on the acceptance of the 4 operations in
Ken's design. MOTION: Adopt definitions of instructions per Ken Parker's
e-mail dated 10/20/95 and presentation verbiage as supported by circuit
diagram. Seconded. Aye: 17. Nay: 0. abstention: 0. Unanimous approval.
SUMMARY: Ken Parker presented a modified analog boundary-scan design of the
one in Draft D05 to minimize the instruction count. The new design allows
one EXTEST instruction, the definition of which was expanded, for both
1149.1 and P1149.4 tests.
Variable Vref - How might we support it?
Steve Sunter's variable Vref.
Refer to Steve's handouts for the following discussion. Viewgraph 2: We've
agreed to include an optional variable Vref and mandate one which is
constant-level. Ken had problem with the second tick under the first
bullet. Steve agreed to cross it out. He also deleted the third tick mark.
Vmin and Vmax are pin specific. After some debating, the following motion
was on the floor.
MOTION: For each pin there shall be a mandatory DC Vref, between Vmin and
Vmax. Seconded. Aye: 17. Nay: 0. Abstention: 1. Motion carried.
For the second bullet on the same viewgraph 2, Steve asked the Working
Group to agree to the motion that variable Vref may be connected but how
it's connected can be discussed later. Further discussion resulted in
brackets being put around the two tick marks underneath the bullet. The
proposal is: Yes, we'll make provision for a variable Vref. This is to
allow for cases where Vref needs to be adjusted for proper operation. Mehdi
questioned if we are accomplishing anything by passing this motion because
the reference can come from off-chip and can be programmed to anything we
wanted. But Steve said this is just for having Vref. The discussion quickly
turned into that of the conceptual comparator. Mehdi actually was concerned
about the possibility of the Vref being interpreted as an actual bandgap
on-chip reference. Ken said to think of it as a 1-bit A/D. Ken asked what
instruction we are talking about here. If EXTEST, then we must have a Vref.
Lee suggested getting rid of the word "Vref." Adam urged the Working Group
to just talk about the concept, not the actual wording which will be taken
care of by Brian in the draft.
Dan said just to call it a 1-bit A/D, but Steve said this is not addressing
the fact that we need a level above which we can call high and below which
we can call low. Tom Fisher said this is not a conceptual function, it's a
REAL function. Steve said the issue here is whether we should have a fixed
Vref and/or variable one. Mehdi originally initiated a motion on this
proposal but later withdrew it.
SUMMARY: A motion was passed to mandate the existence of a constant-level
Vref between Vmin and Vmax at each pin for test purposes. Provision was
made for the capability to adjust the Vref level as necessary.
Differential cells
Steve Sunter's differential pins.
The reason for differential pins is to make accurate measurements in spite
of noise. The possibility of reducing area also exists. A question might
be: Can differential measurements be made with only 2 wires. The answer is
"yes." Steve stipulated that we need identical signal paths for AB1 and
AB2. If accuracy is not needed, use single-ended testing. Are the benefits
worth 2 extra analog bus pins? Only for ICs with lots of differential pins.
How different are 2 and 4 wire switch schemes? Same, except drive pins to
opposite logic levels in interconnect mode.
Viewgraph 4: Both resistors must be matched for the 2 paths to appear the
same during test. However, these resistors need not be in the path during
normal operation. Proposal: If differential pins can be accessed by the
analog bus, then series resistances should be matched for each bus path
(for 2- or 4-wire analog bus). Ken said the Standard should provide
guidelines for designers since designers may not have thought of all of the
implications. Steve mentioned that this matched-resistor design is
consistent with Kelvin measurement which was discussed in the last Working
Group meeting. The driving path should be different from the measuring path
so that the ESD resistors would not affect the measurement, but, the
resistors must be matched to have accurate differential measurements. The
point is to measure the voltage actually present at the pin, excluding the
effects due to the ESD resistors. The circled resistors all have to be
matched (all 4 resistor values should be the same since the pairs of pins
are just copies of each other). Mehdi and others were still not clear about
what problem we're trying to solve here. Ken suggested anyone who does not
completely understand the motivation behind the proposal should abstain
from voting.
Viewgraph 5: The 4-wire bus design was conceived with the intention of
minimizing the overhead. This is slightly different from the one presented
in the last meeting.
Proposal: Differential pins may be accessed by a 4-wire analog bus: -ve
pins accessible via AT1N & AT2N, pin pairs driven to opposite logic values,
and pin pairs "guarded" to same DC reference voltage.
There is an ABM (Analog Boundary Macro) for the input case and another ABM
for the output case.
Keith Lofstrom mentioned we need to take into account both the
possibilities of differential and single ended measurements. More
discussion on e-mail.
MOTION on the above proposal: If 4-wire analog bus, then there shall be:
-ve pins accessible via AT1N & AT2N, pin pairs driven to opposite values,
pin pairs "guarded" to same DC reference voltage. Aye: 8. Nay: 2.
Abstained: 4. Motion carried.
Before voting Keith wanted the voting to be deferred until after the
Working Group has an opportunity to discuss this over e-mail but he was
assured a chance to overturn this by vote next time. Keith opposed it
because of lack of controllability of the Vh and Vl.
MOTION: If differential pins can be accessed by the analog bus, then series
resistances shall be matched for each bus path (for 2- or 4-wire analog
bus). Aye: 7. Nay: 1. Abstention: 4. Motion carried.
SUMMARY: Steve proposed and had the Working Group pass a motion concerning
a way to make accurate differential measurements in the presence of ESD
resistors and another motion for accessibility of 4-wire bus.
IIC - Formal Response
Frans de Jong: IIC - formal response
The following discussion was presented using slides: IIC-01, IIC-02,
IIC-02a, IIC-03, IIC-04, IIC-04a. IIC busses are being used for testing at
Philips. Philips does have chips with both 1149.1 and IIC busses on them.
Question: Can IIC be used to test 1149.1 chips. Answer: Yes, but it would
require extra design efforts and separate test circuits from control
circuits. Normally, IIC usage requires an IC to be in some sort of
functional mode. Also because of this, when IIC busses are used for
testing, together with 1149.1 chips, it often means having to split up the
test into several steps. For this reason it is not recommended as a general
strategy. Keith Baker previously had said it's possible Philips will use
P1149.4, controlled by IIC. This will not happen as we see it now. When
appropriate, P1149.4 will be used as the standard defines. IIC is used for
functional control and sometimes used as an aid in testing. Mani pointed
out that another European company also has chips with IIC and 1149.1 on
them and faces a similar situation.
Frans also showed a photograph of a mixed-signal tester on a single board
SIMM with an ARTEMIS chip in it. This board is being used in systems. The
next step is to put the entire board on a single chip. Frans also indicated
that he could serve as a liaison between the Working Group and ARTEMIS.
The photograph shows a picture of the prototype of a mixed-signal test
module made by MAZeT GmbH. This is a result of one of the mixed-signal
investigation projects (this one partially funded as ESPRIT Project 6138).
This module fits in a simm socket and can perform mixed signal tests. The
exact description can be found in the datasheet. The big QFP in the middle
is the actual ARTEMIS chip, containing a 8051-like core, some additional
digital I/O, containing a TAP for controlling Boundary-Scan tests, AT1 and
AT2 pins, again to be used as controller and eight analog pins, four as
multipxed inputs and four as outputs. The AT1 and AT2 pins are connected
through a '.4 5-switch' arrangement for performance measurements on this
circuit.
The eprom is temporarily placed in a socket. This eprom contains the test
program for the target board. The chip at the other side is the RAM.
Basically this module performs as a simple test module for board level self
tests. For production tests it might help in combination with an external
tester (the module supports slave mode).
Later versions of the module are planned to be smaller and 'affordable'.
For more information:
Grunert@mazet.de
Krellner@mazet.de
IC progress report
Test chip update: Keith Lofstrom.
Steve Dollens is manufacturing the test chips and will distribute test
chips, demo boards, and software. Mani is working on menu-driven software
for the demo board; is responsible for test distribution via WWW; and
setting up an FTP software site at the UW web site; and also collecting
user feedback. Ken is handling BSDL. Keith will create a simplified block
diagram for test purposes. Al Heiden will verify test plan before its
release. Types of tests are shown on the viewgraph and handouts and are
self-explanatory. The differential amplifier has a gain of 5, and operates
at 100MHz. Steve will create a few hundred samples. Keith commented that he
wanted to build an imperfect differential amp so we can test it out using
our scheme. A lot more can be learned testing a bad chip than a good one.
Internal Control Cells
Charles Meyerson's proposal for internal control cells.
There are 3 options for designing internal analog test cells:
1. Leave it to designer's discretion. The result is no software assistance.
2. A few simple rules (have enough rules to allow software to keep track of
which nodes are on ATn, give warning for multiple nodes on ATn; graphical
interface to control switches will help). Minimize overhead allowing
flexibility. Result is that software can aid IC test.
3. Restrictive rules -- designers will ignore them, but rules will be
uniform.
Page 5 of handout/viewgraph: Ken Parker suggested this could be a part of
boundary-scan register, but Brian said this is for internal test. The
reason for Ken's suggestion is that internal test cells being a part of the
boundary-scan register allows one to control everything (including the bits
in the boundary-scan register). The current BSDL does not support anything
other than EXTEST, BYPASS, and SAMPLE.
Proposal for Option 2 was discussed initially. This proposal included the
following slides: Rule 2.1, Rule 2.2, and Rule 2.3. After some discussion,
Proposal for Option 1 was on the table for voting. Ken wondered if people
know what "in accordance with 1149.1" in viewgraph 3 means. Lee Whetsel
suggested adding "in response to private instruction" after "operate." But
Ken again said we could put this in the boundary-scan chain and use
"disable" to disconnect mission circuit and it would allow one to load the
desired bit patterns in there to do specific internal testing. Charles said
we need to have switches so we can access internal nodes for internal
testing.
Proposal for Option 1: MOTION: Internal scan chains that operate in
conjunction with ATn for the purpose of internal analog testing shall
function in accordance with 1149.1 but otherwise are left to the IC
designer's discretion. Seconded. Aye: 14. Nay: 1. Abstention: 0. Motion
carried.
SUMMARY: For internal analog testing, the Working Group does not impose
restrictions but does require internal testing to be compatible with
1149.1. Ken suggested maybe we can work the internal testing aspect into
the boundary-scan scheme.
Draft D05 progress report
Brian Wilkins' draft:
Brian asked how many people have access to WordPerfect? Almost everybody
has access to Word, and SPAsystem. Adam suggested asking the Working Group
to purchase an Adobe software package for Brian. Brian can then generate a
postscript files and convert them to PDF format for posting on the
SPAsystem. The Working Group currently has about $2000 in reserve. Brian
said he can generate a postscript file and will experiment with this. If
the Adobe distiller works, we can get into a cycle. The Working Group
probably would want to avoid conversion between Word, WordPerfect or any
other software packages.
MOTION: The Working Group authorize Adam to buy software for Brian.
Seconded. Unanimous approval.
Cost calculations for adding P1149.4
16. Cost calculation -- Steve Sunter:
Steve presented a paper which he will give at ITC. The version for ITC is a
lot more general than shown here.
Area and cost impact of adding P1149.4 to chip:
Viewgraph 7. First layout assumptions: Assume pads side by side. When
adding P1149.4, there will be some additional circuitry at each pin
resulting in a net increase of 1 extra pad length in both x and y
directions.
Viewgraph 8. Assumptions list. Assuming we don't have to go to the next
larger-size package. These prices are reasonable. The idea behind all this
work is so that we can convert area to cost.
Viewgragh 9. The most cost will be in adding 1149.1 on chips. Next is
"adding 1149.1, but die not pin limited." Third is the case where we
already have 1149.1 and only want to add the 2 little extra pins.
Viewgraph 10. Focusing on just the top curve of viewgraph 9: A small
increase in area for TAP controller. But the big killer is adding extra
pins. Steve Dollens interjected, saying in some cases that may be a
blessing.
Viewgraph 11. Looking at cost increase. When we get to the large die sizes,
the cost goes up (see graphs). It is most pronounced for the extreme case
of no 1149.1 pins. Above half-inch, the cost escalates. This is why high
volume, complex chips are fabbed in the 200-400 mil range.
SUMMARY: The main contributor to cost is adding extra pins. An increase in
area corresponds to an increase in cost.
Balloting schedule
Balloting schedule.
On handout, change "vendors" to "pushers," and "system designers" to
"users." Also add "6. others".
Adam noted that there have been drop-outs as well as newcomers.
Time -1: Develop ballot list, prep balloters.
Time 0: Send out draft for ballot (to all 257 on the list?)
+3 months: Receive votes.
+3 months: Respond to comments/negative votes and re-send ballot.
+3 months: Results go to IEEE before next board meeting.
+2 months: Final standard.
Mani suggested perhaps set time 0 to 5/96. We need to set a goal in order
to make the projected milestones. Or maybe we still need to know what
1149.1's position is. Still we need to set a target date. Some in the
Working Group don't believe in setting a date. Question posed to Brian is:
Assume 1149.1 somehow could make it go faster, then can we get a draft to
vote on in May? Lee said that 1149.1 is a reasonable group and should vote
on this soon. Adam said we need to have something to review before sending
draft out.
1149.n updates
1149.n updates:
No one really knew what was going on in P1149.2 except that the P1149.2
Working Group adopted the TAP.
1149.5 was approved by IEEE in July, 1995. Document is now available from
IEEE. 1149.5 also accepted by VME64 bus. There are 2 papers about 1149.5 at
ITC.
Next meeting in Scotts Valley, CA in February, 1996
Next meeting:
Terry Junge has volunteered for SEAGATE to sponsor the next Working Group
meeting in February, 1996. The format will be split-date. Need to decide on
the day (Thursday-Friday?). In terms of publicity, do we want to advertise
at ISSCC next year? We will have no exposure at ISSCC. Keith doesn't have
silicon so he will have no paper at ISSCC. Anybody can get in CICC. Debate
over the meeting dates ensued. Finally, it was decided to vote on the 2/96
Working Group meeting dates over e-mail.
Before adjourning, the subgroup on 1149.1/P1149.4 set up a date and time to
meet: After the Plenary Session in the back of the hall.
Adjourn
MOTION: Adjourn meeting. Seconded. Approved.
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Access the Minutes of the February, 1996 Working Group Meeting.
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To reach the Chair of the IEEE P1149.4 Working Group:
Adam Cron
Motorola
50 East Commerce Drive, Suite M5
Schaumburg, Illinois 60173
USA
Phone: (847)576-3092
Fax: (847)538-4801
E-mail: adam_cron@wes.mot.com